1. Field of the Invention
This invention relates to a semiconductor light emitting device and a semiconductor light emitting apparatus.
2. Background Art
Flip-chip semiconductor light emitting devices are being developed for devices such as LEDs (Light Emitting Diodes) as structures promising high heat dissipation and high light extraction efficiency. In such structures, the light emitting layer side of the wafer contacts the heat sink, and the emitted light is extracted from the substrate side directly or by reflections by a reflecting film.
Technology for forming high-efficiency reflecting films is essential for flip-chip semiconductor light emitting devices. Silver and aluminum are drawing attention as reflecting film candidates to realize light emitting devices of high luminance by efficiently reflecting light produced by the light emitting layer, particularly light in the ultraviolet band.
Silver particularly provides ohmic contact with a p-type nitride semiconductor layer and is utilized in flip-chip semiconductor light emitting devices as p-side electrodes/reflecting films. However, aluminum having high reflecting characteristics does not exhibit ohmic properties, and electrical characteristics are therefore sacrificed.
Conversely, a structure in JP-A 2005-116794 (Kokai) attempts to realize both electrical characteristics and reflecting characteristics using subdivided ohmic electrodes provided on a contact layer with reflecting layers formed therebetween.
Generally, in the case where light emitted inside a flip-chip semiconductor light emitting device is extracted to the exterior, the light extraction efficiency is better as the light emitting region is proximal to the central portion of the semiconductor light emitting device. The more proximal to the central portion, the lesser the effects of the device end face, and therefore the better the light output reproducibility. On the other hand, to increase the light extraction efficiency, it is advantageous to design a large reflecting region of the electrode formation surface, and it is desirable to provide reflecting regions also in regions other than the central portion. In other words, a tradeoff exists in providing the light emitting region in the central portion of the device and making the reflecting region as large as possible, and limitations have been reached for improving both at the same time.
Conventional art such as JP-A 2005-116794 (Kokai) has not sufficiently investigated planar configurations of ohmic electrodes and reflecting films. There is room for improvement of light extraction efficiency and light output reproducibility.